Neanderthal DNA has subtle but significant impact on human traits

February 11, 2016
Neanderthal DNA influences many physical traits in people of Eurasian heritage. Credit: Michael Smeltzer, Vanderbilt University

Since 2010 scientists have known that people of Eurasian origin have inherited anywhere from 1 to 4 percent of their DNA from Neanderthals.

The discovery spawned a number of hypotheses about the effects these genetic variants may have on the physical characteristics or behavior of , ranging from skin color to heightened allergies to fat metabolism... generating dozens of colorful headlines including "What your Neanderthal DNA is doing for you" and "Neanderthals are to blame for our allergies" and "Did Europeans Get Fat From Neanderthals?"

Now, the first study that directly compares Neanderthal DNA in the genomes of a significant population of adults of European ancestry with their clinical records confirms that this archaic genetic legacy has a subtle but significant impact on modern human biology.

"Our main finding is that Neanderthal DNA does influence clinical traits in modern humans: We discovered associations between Neanderthal DNA and a wide range of traits, including immunological, dermatological, neurological, psychiatric and reproductive diseases," said John Capra, senior author of the paper "The phenotypic legacy of admixture between modern humans and Neanderthals" published in the Feb. 12 issue of the journal Science. The evolutionary geneticist is an assistant professor of biological sciences at Vanderbilt University.

Neanderthal-influenced traits. Credit: Deborah Brewington, Vanderbilt University

Some of the associations that Capra and his colleagues found confirm previous hypotheses. One example is the proposal that Neanderthal DNA affects cells called keratinocytes that help protect the skin from environmental damage such as ultraviolet radiation and pathogens. The new analysis found Neanderthal DNA variants influence skin biology in modern humans, in particular the risk of developing sun-induced skin lesions called keratosis, which are caused by abnormal keratinocytes.

In addition, there were a number of surprises. For example, they found that a specific bit of Neanderthal DNA significantly increases risk for nicotine addiction. They also found a number of variants that influence the risk for depression: some positively and some negatively. In fact, a surprisingly number of snippets of Neanderthal DNA were associated with psychiatric and neurological effects, the study found.

"The brain is incredibly complex, so it's reasonable to expect that introducing changes from a different evolutionary path might have negative consequences," said Vanderbilt doctoral student Corinne Simonti, the paper's first author.

According to the researchers, the pattern of associations that they discovered suggest that today's population retains Neanderthal DNA that may have provided modern humans with adaptive advantages 40,000 years ago as they migrated into new non-African environments with different pathogens and levels of sun exposure. However, many of these traits may no longer be advantageous in modern environments.

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Credit: Michael Smeltzer, Vanderbilt University

One example is a Neanderthal variant that increases blood coagulation. It could have helped our ancestors cope with new pathogens encountered in new environments by sealing wounds more quickly and preventing pathogens from entering the body. In modern environments this variant has become detrimental, because hypercoagulation increases risk for stroke, pulmonary embolism and pregnancy complications.

In order to discover these associations, the researchers used a database containing 28,000 patients whose biological samples have been linked to anonymized versions of their electronic health records. The data came from eMERGE - the Electronic Medical Records and Genomics Network funded by the National Human Genome Research Institute - which links digitized records from Vanderbilt University Medical Center's BioVU databank and eight other hospitals around the country.

This data allowed the researchers to determine if each individual had ever been treated for a specific set of medical conditions, such as heart disease, arthritis or depression. Next they analyzed the genomes of each individual to identify the unique set of Neanderthal DNA that each person carried. By comparing the two sets of data, they could test whether each bit of Neanderthal DNA individually and in aggregate influences risk for the traits derived from the medical records.

"Vanderbilt's BioVU and the network of similar databanks from hospitals across the country were built to enable discoveries about the genetic basis of disease," said Capra. "We realized that we could use them to answer important questions about human evolution."

According to the evolutionary geneticist, this work establishes a new way to investigate questions about the effects of events in recent human evolution.

The current study was limited to associating Neanderthal DNA variants with physical traits (phenotypes) included in hospital billing codes, but there is a lot of other information contained in the , such as lab tests, doctors' notes, and medical images, that Capra is working on analyzing in a similar fashion.

Explore further: Sunlight adaptation region of Neanderthal genome found in up to 65 percent of modern East Asian population

More information: "The phenotypic legacy of admixture between modern humans and Neandertals," by C.N. Simonti et al. science.sciencemag.org/cgi/doi/10.1126/science.aad2149

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7 comments

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NoStrings
5 / 5 (2) Feb 11, 2016
Interesting. But, have you made a comparison with people of strictly African origin that don't have Neanderthal DNA mixed in?
I see that the skin - keratosis (and melanoma) resistance - checks as stated. But, how about all other issues you mentioned? Any statistics that any practicing MD could contribute here? For example - addiction to tobacco should be easy to check.
Zorcon
1.7 / 5 (6) Feb 11, 2016
We need more data, we have the technology to get it, and it won't cost the taxpayers a cent.

We have most of the Neanderthal genome sequenced. In vitro fertility clinics discard excess embryos every day; why let them go to waste? And we have the technology (CRISPR). Here's the plan:

1) Extract totipotent stem cells from xx & xy embryos.
2) split into 2 groups of each sex:
-In group A, replace genetic material with Neanderthal sequences.
-Leave group B as is.
3) Recruit young women for a new Realty TV show, "I Gave Birth to a Neanderthal!".
4) Implant one A and one B into each star (each mother will carry same sex twins, 1 Neanderthal and 1 modern human).

The TV show will pay for the experiment and run for one season, culminating in the births.

5) Each pair of twins will be adopted & raised together to control for environmental effects.

After that, the spin offs start:
"The Girl From 50,000BC"
"Leave It To Thag"
"Neanderthals: The Next Generation.
BartV
2.5 / 5 (4) Feb 11, 2016
Zorcon---wow your proposal reeks of Nazism.

Zorcon
2 / 5 (5) Feb 12, 2016
Zorcon---wow your proposal reeks of Nazism.


Umm, let me guess... because the first Neanderthal bones were discovered in Germany?

HTK
2.3 / 5 (3) Feb 12, 2016
Is it not obvious with sunken eyes, broad shoulders, body hair, stronger muscles, neaderthals have passed onto the caucasian genetic traits?
Torbjorn_Larsson_OM
5 / 5 (2) Feb 12, 2016
@HTK: Not obvious, since the found alleles are so heterogeneous (~2 % of alleles, but the sum makes up ~ 20 % of a neanderthal). The article finds Neanderthal alleles that have medical noticeable effects in enough individuals. Likely there are more such that has noticeable effect, but if they affect eye sockets et cetera is likely unknown.

Dunno if we know what body hair they had, though I think higher muscle strength is observable from tendon attachments et cetera.
Zorcon
1 / 5 (1) Feb 13, 2016
Neanderthal Breeding Project (continued):

Once we've bred enough of them we can test them for psychological traits.

Might they have more resistant to indoctrination than modern humans? Perhaps they were just better at rational thinking. If so, that might explain why they died out: they lacked the superior traits that make us so good at genocide. They may simply have been unable to incorporate religion and Political Correctness into their worldviews. It would also be fascinating to know if Neanderthals lacked a sense of humor, like some people nowadays.

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